Candidate: Aubree Gordon, PhD, MPH is an Assistant Adjunct Professor and an Assistant Researcher at the University of California, Berkeley (UCB). Career Development Plan: Dr. Gordon will conduct vital research on the epidemiologic features of influenza in Nicaragua, a tropical country. The objective of this project is to expand knowledge of influenza in tropical countries in order to provide evidence for the need for interventions and knowledge for the design of interventions. Additionally, this K02 award will provide the candidate with protected time for her research program in order to ensure her continued successful development as an independent researcher and leader in global health. Project: The program will be divided into two related projects: Project 1 will focus on the epidemiology and phylogenetic characterization of pediatric influenza in a prospective cohort, and Project 2 will consist of a household transmission study of influenza. Within Project 1, the burden and seasonality of influenza in the cohort will be examined in Aim 1. Individual demographic and medical risk factors as well as socio- demographic risk factors for influenza virus infection and influenza severity will be characterized in Aim 2. In Aim 3, the evolutionary dynamics of influenza A virus will be evaluated over time and space, including an investigation of intra-host diversity, using viruses obtained from both the cohort study and the household transmission study. In the household transmission study in Project 2, 222 households with an index case of influenza will be followed for 9 days. Serum and respiratory samples will be collected from all household contacts to investigate parameters of influenza transmission in a developing country setting and to examine individual and household risk factors that affect influenza transmission and disease severity. Basic influenza transmission parameters, including the secondary attack rate and serial interval, will be calculated in Aim 4. The effect of household and individual characteristics on influenza transmission will be determined in Aim 5. Finally, the proportion and determinants of asymptomatic influenza infection will be examined in Aim 6. Mentorship: Primary mentorship will be provided by Dr. Eva Harris at UCB and by Dr. Angel Balmaseda at the Ministry of Health in Nicaragua. Dr. Harris is a virologist and reknowned for her work in scientific capacity building in under-resourced settings. Dr. Angel Balmaseda is a virologist and head of the Nicaraguan National Laboratory, Centro Nacional de Diagn ?stico y Referencia. Dr. Arthur Reingold will serve as a co-mentor. Dr. Reingold is a specialist in infectious disease epidemiology, with topic areas that include the epidemiology of influenza, pediatric respiratory diseases and vaccines. Pulbic Health Relevance: This proposal is well- positioned to have substantial impact because of the lack of knowledge of the epidemiology, and transmission of influenza in tropical countries, which the proposed studies will address.